Field of the Invention
The present invention relates to a laser processing apparatus for applying a laser beam to a wafer to thereby form an ablation groove on the wafer.
Description of the Related Art
A plurality of devices such as ICs and LSIs are formed on the front side of a wafer so as to be separated by a plurality of division lines. The wafer is divided into the individual devices by using a laser processing apparatus to apply a laser beam along the division lines and thereby form an ablation groove on the front side of the wafer along each division line. The individual devices thus obtained are used in various electronic equipment.
The laser processing apparatus mentioned above includes a chuck table for holding the wafer, laser beam applying means having focusing means for applying the laser beam to the wafer held on the chuck table, feeding means for relatively feeding the chuck table and the laser beam applying means in an X direction, indexing means for relatively indexing the chuck table and the laser beam applying means in a Y direction perpendicular to the X direction, an imaging unit for imaging a work area, and a controller. With this configuration, an ablation groove can be formed with high accuracy on the wafer by applying the laser beam along each division line having a width of about 50 μm, for example (see Japanese Patent Laid-open No. 2006-245467, for example).
Such an ablation groove along each division line is formed in the case of dividing the wafer into the individual devices from this groove as a division start point (see Japanese Patent Laid-open No. 2007-19252, for example) or in the case of removing low-permittivity insulator films (low-k films) stacked on each division line (see Japanese Patent Laid-open No. 2007-173475, for example). In any case, the devices are formed adjacent to the division lines. Accordingly, the ablation groove must be formed inside each division line so as not deviate from the width thereof.